Part II – The Philosophy of Time Travel

Lost, Fringe, Doctor Who, Star Trek, The Flash, Harry Potter, Legends of Tomorrow, even Game of Thrones. Why do so many of the stories we love involve time travel?


What is time?

The concept of time is, in many ways, the feature that lends gravitas to every story ever told. The ticking of the clock follows us wherever— and whenever— we go. We consider time wistfully when looking to the past; anxiously or excitedly when anticipating the future; even contentedly, when meditating on a continuous present. Time is what makes life meaningful; memories across time are what make us, us.

Time defies all description and definition. In his book Physics of the Impossible, theoretical physicist Michio Kaku notes that time is “not possible” because “the past is gone, the future does not exist, and the present exists only for an instant.” As such, we are forced to resort to metaphor to explain time— and, interestingly enough, most (if not all) of these phrases normally refer to objects in space: time flies, time flows, time crawls. Time moves, tautologically, in respect to itself.

Time is what makes life meaningful.

But is time travel possible? Einstein’s theory of relativity proposed that time is a relative concept, inspiring the proliferation of the term “spacetime.” This, in turn, yielded a neat idea: If we can travel in space, and space shares similar properties with time, what’s to say we can’t travel in time?

Thanks to the theory of relativity, certain types of “time travel” are already a fait accompli. Time moves ever so slightly faster at the center of Earth’s gravitational pull, so astronauts in orbit far above Earth’s surface age more slowly than terrestrial-bound humans. Because of this time dilation effect, astronaut Sergei Krikalev, who spent 803 days, 9 hours, and 39 minutes in space, technically traveled 0.02 seconds into his own future over the course of his space travel. And in 2014, physicists successfully simulated photons traveling through time while experimenting with the intersection of Einstein’s cosmological theory of stars and planets and the nanoscopic world of quantum mechanics.

If we can travel in space, what’s to say we can’t travel in time?

The most promising time travel theory piggybacks on what Einstein proposed more than a century ago, positing that the hypothetical existence of wormholes could serve as a bridge not only through space, but through time as well. Kip Thorne was one of the first to devote serious research to the practical connection between wormholes and time travel.  Nowadays, most physicists concede that they have yet to discover a physical law that explicitly prohibits traveling in time— so it’s not impossible per se, merely very, very improbable.

A model of “folded space” proposes a way to also “fold” time, making it possible to travel to a different time via a wormhole.

(For more on Kip Thorne, wormholes and the actual physics of time travel, check out

The Grandfather Paradox and the Philosophy of Time Travel.

While physicists attempt to tackle the overarching practicality of time travel, philosophers deal with matters of logical consistency. (For a deep dive into the philosophy of time travel, the Stanford Encyclopedia has got you covered.) David Lewis, known for his rendition of the time travel-centric “grandfather paradox,” was philosophy’s best-known champion of time travel until his death in 2001. In his famous paper “The Paradoxes of Time Travel,” Lewis spells out the paradox like so: Tim wants to go back in time to kill his grandfather as a young man. But if Tim succeeds and his grandfather dies before he meets Tim’s grandmother, then Tim will never be born, and therefore will not be able to go back in time and kill his grandfather in the first place.

This paradox has puzzled time travel enthusiasts for ages, but Lewis proposes a solution: Even if Tim can kill his grandfather— that is, he has a time machine, a rifle, two hands and a clear shot— he won’t, because he already didn’t. Infuriating, perhaps, but elegantly simple, hanging on two different meanings of the word “can.”

“‘Can’ is a word of possibility, and possibility comes in different grades,” Richard Hanley, professor of philosophy at the University of Delaware, explains. “We flip around between these grades without contradicting it.”

We experience this phenomenon even without the added wrinkle of time travel, Hanley notes. “There are certain things that you’ll try to do today that you’ll fail to do,” he says. “Why? Not because there’s some ‘time police’ to stop you from doing things, but because something ordinary stops you.” We may be in an unusual epistemological position in the case of time traveling Tim, but Hanley says that it would be something similarly mundane that foils Tim’s mission— his gun jams, he gets distracted, perhaps he develops a conscience. In short, he won’t kill his grandfather, because he didn’t.

The idea that space and time could be connected emboldened time travel enthusiasts within the physics community and had a revitalizing effect on philosophers who hold an eternalist view of time. Eternalists like Hanley and Lewis view all points in time— rather than just the present moment— as equally “real,” the same way that all points in space are considered equally real.

“In order for me to talk to you in California,” Hanley says, “it would be plausible to say that California has to be there! It’s not like, when I’m wandering around, the only place that exists is the place that I’m actually at.”

Even if Tim can kill his grandfather, he won’t, because he already didn’t.

The eternalist view of time, Hanley points out, gets a good deal of support from people in disciplines as seemingly disparate as modern physics and medieval theology. “The other nice thing about it,” he says, “is that it’s a particularly friendly view to time travel.”

Check back in next week for a discussion of two popular, plausible time travel theories and thoughts from Damon Lindelof (Lost, The Leftovers), Marc Guggenheim (Legends of Tomorrow) and Terry Matalas (12 Monkeys). Or, you know, just hop in your time machine and read it now. If you choose that option, hit me up, I have some questions…


Part I – Time Travel: The Story with a Thousand Faces

Lost, Fringe, Doctor Who, Star Trek, The Flash, Outlander, Legends of Tomorrow, even the Harry Potter play. Why do so many of the stories we love involve time travel?

An overview.

Half a century ago, Gene Roddenberry’s Star Trek declared space “the final frontier.” Now, as the beloved sci-fi series gears up for a reboot, the final frontier is just about visible on the horizon: NASA expects to send astronauts to Mars by 2030, while SpaceX intends to colonize the Red Planet in this lifetime. Certainly, space travel is still a burgeoning field of real-world scientific study, and the stars still beckon us upward in fiction as well.

But there is another dimension of the cosmos that science has yet to crack open, a concept of exploration that rose in popularity with Albert Einstein’s theory of relativity and ensnared our cultural imagination for many years to come: time travel.

When Einstein published his theory of relativity at the dawn of the twentieth century, he shattered previously held notions about the complex nature of our physical world. Of course, time travel stories existed well before Einstein, as in, most famously, H.G. Wells’s 1895 novel The Time Machine. But Einstein’s notions about temporal dilation galvanized the creative community to delve more deeply into the moral, physical, and psychological implications of traveling through time, setting the stage for a century of time machines, time ships, time turners, TARDISes and more.

This pilot season, three time travel-centric shows on three separate networks were given the green light.

As time travel fiction branched out toward film and television in the mid-twentieth century, certain science fiction touchstones emerged. Gene Roddenberry’s Star Trek contains nearly as much time travel as space travel (indeed, the two are often one and the same), and is responsible for exploring several different iterations of the time travel trope over the course of its five television series and 13+ films. This year marks the fiftieth anniversary of the original series, a milestone celebrated with the announcement of an upcoming addition to the Star Trek canon in the form of a 2017 series airing on CBS, from showrunner Bryan Fuller.

Another time travel classic is currently undergoing a renaissance: Terry Gilliam’s 1995 cult film 12 Monkeys, starring Bruce Willis as a time traveler intent on preventing the outbreak of a virus that devastates humanity. The tech-noir film is known for its bleak consideration of fate and free will. But it also has earned its place in cinematic history as a remake of the French New Wave classic, Chris Marker’s La Jetée, which itself was an homage to Alfred Hitchcock’s masterpiece, Vertigo. In 2015, 12 Monkeys made the leap to television, and the Syfy series— developed by Terry Matalas and Travis Fickett— wrapped up its second season in July.

These are only two examples of Hollywood’s time travel fascination, which is making itself right at home on the small screen. Legends of Tomorrow, featuring a ragtag group of misfits chasing an immortal villain across time, began its run on the CW in late January. 11.22.63, Hulu’s adaptation of Stephen King’s JFK-themed time travel novel, debuted on Presidents Day, and Starz predated both of those shows with Outlander, based on Diana Gabaldon’s best-selling book series.

This pilot season, no fewer than three time travel-centric shows on three separate networks were given the green light: Timeless on NBC, from Supernatural creator Eric Kripke and The Shield creator Shawn Ryan; Fox’s Making History, a comedy from Phil Lord and Chris Miller of The Lego Movie fame; and ABC’s Time After Time featuring Freddie Stroma as H. G. Wells. And hey, even the stage has snagged a time travel tale in the form of J. K. Rowling’s latest addition to the Harry Potter canon: Harry Potter and the Cursed Child.

The trend highlights a truth universally acknowledged by legions of science fiction fans: All the best stories are time travel stories.

The evidence has presented itself on television screens for decades, hearkening back to the most memorable episodes of sci-fi classics, many of which utilize time travel to tell their tales. Who could explain the beauty of Lost without referencing Season Four’s “The Constant”? How would Fringe have ended if it weren’t for the popularity of the Season Two episode “White Tulip”? What catapults “The City on the Edge of Forever” to the top of nearly every Star Trek list? And is there a Doctor Who fan who hasn’t tried to indoctrinate someone by making them watch “Blink”?

It is a truth universally acknowledged that all the best stories are time travel stories.

Stories involving time travel resonate on a multiplicity of levels, and for a multiplicity of audiences. Some time travel tales illuminate the meaning of personal choices and identity, as time-based emotions like hope and regret (one looking forward, the other looking back) are thrown into sharp relief for characters that can fast-forward and rewind their own stories.

Time travel allows for the wrangling of personal and macro histories, whether you wish to ponder the implications of killing Hitler or to explore a life in which you had attended a different college. Many time travel enthusiasts merely enjoy the tantalizing allure of brain-busting cosmological paradoxes. (If you want to keep a time travel nerd busy for days, ask them to disentangle the plot of Looper, Primer or X-Men: Days of Future Past.) And when it comes to love— that prototypical “tale as old as time”— time travel is uniquely able to magnify the theme of a star-crossed relationship.

In 1990, Stephen Hawking— our latter-day Einstein— scoffed at the notion of time travel and famously declared: “If time travel is possible, where are the tourists from the future?” But he has since softened his view on the subject matter, and the debates he has fueled within the scientific community have whetted the public’s appetite for time travel over recent decades. In fact, time travel has become such a prevalent subject that everyone seems to be attempting to drag it into their own corner.

Time-based emotions like hope and regret are thrown into sharp relief for characters that can fast-forward and rewind their own stories.

Kip Thorne, the scientist who consulted on Christopher Nolan’s Interstellar, famously hurled down the gauntlet as time travel stories rose in prominence at the turn of the century. “Physicists have realized,” he declared, “that the nature of time is too important an issue to be left solely in the hands of science fiction writers.”

Fortunately for us, science fiction writers are more than up to the task.

Check back in next week for a consideration of the logical and philosophical  (im)possibilities of time travel! Or, you know, just hop in your time machine and read it now. If you choose that option, hit me up, I have some questions…